A bar magnet of magnetic moment M and moment of inertia I is freely suspended such that the magnetic axial line is in the direction of magnetic meridian. If the magnet is displaced by a very small angle θ, angular acceleration is magnetic induction of earth's horizontal field is BH)
(a) MBHθ/I
(b) IBHθ/M
(c) Mθ/IBH
(c) Iθ/MBH